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991.
建立了测定食用植物油中23种农药残留的气相色谱–质谱联用方法。采用固相萃取,以乙腈超声提取,经过PSA,C_(18)柱进行净化,用气相色谱–质谱法测定,外标法定量。23种农药在0.01~1.0 mg/L范围内与色谱峰面积线性关系良好,相关系数为0.997 3~0.999 7,方法检出限为5~15μg/kg。测定结果的相对标准偏差为2.25%~9.40%(n=6),加标回收率为78.4%~127.3%,可以满足食用植物油中多种农药残留的同时分析。采用该方法对国内市场常见的食用植物油进行检测分析,所检测的农药残留均在国家标准的限量范围内。 相似文献
992.
A series of Li3V2(PO4)3/C composites with different amounts of carbon are synthesized by a combustion method. The physical and electrochemical properties of the Li3V2(PO4)3/C composites are investigated by X-ray diffraction, element analysis, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and electrochemical measurements. The effects of carbon content of Li3V2(PO4)3/C composites on its electrochemical properties are conducted with cyclic voltammetry and electrochemical impedance. The experiment results clearly show that the optimal carbon content is 4.3 wt %, and more or less amount of carbon would be unfavorable to electrochemical properties of the Li3V2(PO4)3/C electrode materials. The results would provide some basis for further improvement on the Li3V2(PO4)3 electrode materials. 相似文献
993.
994.
Yaru Qin Qian Gao Yanmei Chen Wei Liu Feng Lin XiangFei Zhang Yaping Dong Yahong Li 《Journal of Cluster Science》2017,28(3):891-903
The incorporation of LnIII ions into the 12-metallacrown-4 topology affords the formation of four mixed 3d-4f pentanuclear complexes of compositions [NH(C2H5)3]{[Ln(OAc)4] [12-MC Mn III (N)shi-4]}·xH2O (Ln = Sm (1), Gd (2), Tb (3), Dy (4); x = 0.5 for 1 and 3, x = 0.25 for 2, x = 0 for 4; H3shi = salicylhydroxamic acid). Compounds 1–4 were obtained from the reactions of H3shi with Mn(CH3COO)2·4H2O and Ln(NO3)3·6H2O, in the presence of N(C2H5)3. They all contain a crown-like [Mn4Ln(μ-NO)4]11+ core with four MnIII atoms being at the rim of the crown and an LnIII ion occupying the dome of the crown. The peripheral ligation about the core is provided by four η1:η1:µ acetate groups. The identity of the LnIII ions slightly affects the 12-metallacrown-4 frameworks, as demonstrated by the gradual decrease of the distances between the LnIII ions and the centres of the Mn4 planes (1.85 Å for 1, 1.81 Å for 2, 1.80 Å for 3, and 1.77 Å for 4). Variable-temperature dc magnetic susceptibility studies were carried out on polycrystalline samples of 1–4. Antiferromagnetic interactions are determined for complexes 1–4. 相似文献
995.
Preparation,characterization and properties of fiber reinforced composites using silicon‐containing hybrid polymers 下载免费PDF全文
A novel glass fiber reinforced composite was prepared by using silicon‐containing hybrid polymers, poly(methylhydrogen‐diethynylsilyene) (PMES) and poly(phenylethynyl‐silyloxide‐phenylborane) (APABS), as matrix resins. The curing behavior and rheological properties of the matrix resins were investigated by differential scanning calorimetry (DSC) and rotational rheometer. The dynamic viscoelastic properties, mechanical properties, and microstructures of the composites were studied by dynamic mechanical analysis (DMA), universal testing machine (UTM), and scanning electron microscopy (SEM), respectively. The results show that the composite can be well cured between 200 and 300 °C through reactive groups like Si‐H, N‐H, and C≡C units, the possible thermosetting mechanism is also proposed. The composites exhibit excellent mechanical properties with bending strength reach up to 261 and 178 MPa before and after heat‐treating, respectively. SEM analysis clearly indicates that crack in the matrix, matrix/fiber interface debonding, and fiber pull out are predominate failure mechanism for the composites which are heat‐treated in different temperatures. All these obtained results can give theoretical guiding reference for their further applications. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
996.
Preparation and characterization of anion‐exchange membranes derived from poly(vinylbenzyl chloride‐co‐styrene) and intercalated montmorillonite 下载免费PDF全文
Na Liang Yi Liu Xiaofeng Liao Zhengyuan Luo Dongzhi Chen Xiaohong Liu Hongwei Zhang 《先进技术聚合物》2017,28(6):728-735
In this paper, three organic intercalating agents containing cations [hexadecyl trimethyl ammonium bromide (CTAB), poly(acrylamide‐co‐diallyldimethylammonium chloride), and quaternized polyethyleneimine] are used to prepare intercalated montmorillonites (MMT) by ion‐exchange method. Then the modified MMTs are doped with vinylbenzyl chloride and styrene copolymer [poly(vinylbenzyl chloride‐co‐styrene)] for fabricating composite anion‐exchange membranes (AEM). Fourier transform infrared, X‐raydiffraction, thermogravimetric analysis, scanning electron microscopy, and Mastersizer laser particle size analyzer are employed to characterize the structure and morphology of MMTs and AEMs. The successful intercalation of MMTs is approved, and the MMT intercalated by CTAB shows an interlayer distance of 2.31 nm. The properties of the composite membranes including water uptake, mechanical property, and ionic conductivity are investigated. Among all the AEMs, the composite membrane containing MMT sheets with CTAB demonstrates better compositive performances. It presents an ionic conductivity of 2.09 × 10?2 S cm?1 at 80°C and good alkaline solution stability. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
997.
Gradient polymer networks formed by photopolymerization with self‐floating polysiloxane‐containing nanogel 下载免费PDF全文
Polysiloxane‐containing nanogels can be used as a fast, convenient and environmentally friendly method to control gradient photopolymerization and to obtain gradient polymer network because of its self‐floating feature. The chain length of polysiloxane is a key factor that influences the self‐floating capability of the polysiloxane‐containing nanogel. This paper reports a series of nanogels compositions synthesized with methacrylate‐modified polysiloxanes with different chain lengths, urethane dimethacrylate (UDMA) and isobornyl methacrylate (IBMA) at a molar ratio of 10:20:70 in the presence of a thiol chain transfer agent. The effect of polysiloxane chain length on self‐floating capability of the nanogel and gradient polymer network was researched. The results show that polysiloxane chain length is the main driving force for the self‐floating capability of the nanogels. The nanogel with long polysiloxane chain length exhibits good self‐floating capability in the monomer–polymer matrix because of the lower surface tension of polysiloxane. Furthermore, the gradient polymer network containing the nanogel with long polysiloxane chain length presents lower dispersion surface energy and greater hardness and thermostability. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
998.
A novel method to prepare microcellular poly(vinyl alcohol) foam based on thermal processing and supercritical fluid 下载免费PDF全文
Combining the thermal processing and supercritical fluid technology develops a novel preparation method of microcellular poly(vinyl alcohol) (PVA). Water, as the plasticizer in system, can form the hydrogen bonding with pendant hydroxyl of PVA and weaken its strong intermolecular and intramolecular forces to realize the thermal processing. Supercritical carbon dioxide (sc‐CO2) can easily dissolve into water‐plasticized PVA (WPVA) because of the destruction of crystal region caused by water, and the enhanced sc‐CO2 solubility can greatly improve the foamability of WPVA. The porous structure generates through the saturation of sc‐CO2 in WPVA sample and followed by pressure drop‐induced phase separation. The foaming behavior of WPVA was studied as a function of saturation pressure, foaming temperature, and saturation time. The cell density, cell size, and distribution of the obtained foam can be controlled by tuning processing conditions. The results revealed that the cell size decreased, and its distribution narrowed with saturation pressure increasing, or decrease of foaming temperature. But excessively increasing the saturation time generated a negative effect on the foaming behavior owing to the deteriorated plasticization effect resulted from the loss of water. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
999.
Dr. Chun Fang Ying Huang Dr. Lixia Yuan Yaojun Liu Weilun Chen Yangyang Huang Kongyao Chen Prof. Jiantao Han Prof. Qingju Liu Prof. Yunhui Huang 《Angewandte Chemie (International ed. in English)》2017,56(24):6793-6797
Although sodium-ion batteries (SIBs) are considered as alternatives to lithium-ion batteries (LIBs), the electrochemical performances, in particular the energy density, are much lower than LIBs. A metal–organic compound, cuprous 7,7,8,8-tetracyanoquinodimethane (CuTCNQ), is presented as a new kind of cathode material for SIBs. It consists of both cationic (CuII↔CuI) and anionic (TCNQ0↔TCNQ−↔ TCNQ2−) reversible redox reactions, delivering a discharge capacity as high as 255 mAh g−1 at a current density of 20 mA g−1. The synergistic effect of both redox-active metal cations and organic anions brings an electrochemical transfer of multiple electrons. The transformation of cupric ions to cuprous ions occurs at near 3.80 V vs. Na+/Na, while the full reduction of TCNQ0 to TCNQ− happens at 3.00–3.30 V. The remarkably high voltage is attributed to the strong inductive effect of the four cyano groups. 相似文献
1000.
Danlu Xue Chunyi Liu Xiaomin Li Jie Tang Lihua Cao Yi Liu Zhengping Chen 《Journal of Radioanalytical and Nuclear Chemistry》2017,313(2):419-428
We studied on the structural requirement of C11b chirality of tetrabenazine (TBZ) analogs as vesicular monoamine transporter 2 (VMAT2) ligands. TBZ analogs (2, 6a, 6b) and 18F-radiolabeled [18F]6a and [18F]6b with eliminated C11b chirality were synthesized and characterized. Competition studies demonstrated that 2, 6a and 6b displayed much lower in vivo VMAT2 bindings than TBZ. MicroPET imaging studies of [18F]6a and [18F]6b showed negligible accumulation in VMAT2-enriched regions as compared with the known VMAT2 ligand 18F-FP-(+)-DTBZ. These results suggest that C11b chirality of TBZ analogs is essential for in vivo VMAT2 binding bioactivity. 相似文献